WRKY transcription factors play a role in a variety of biological processes. Several studies have revealed that abiotic stress regulates the transcription of a large number of WRKY genes. In this study, we report the identification of a novel ‘SAPK10-WRKY87-ABF1’ biological pathway, through which they harmoniously enhance drought and salinity tolerance. We generated OsWRKY87-overexpressing transgenic rice and found that the transgenic seedlings exhibited significantly improved drought and salinity stress tolerance. Subcellular localization in rice seedling protoplast revealed that OsWRKY87-GFP fusion protein mostly accumulated in the nucleus, suggesting that OsWRKY87 is a nucleus-localized protein, in line with the predicted function of OsWRKY87 as a transcription factor. In vivo interaction between SAPK10 and WRKY87 was demonstrated by Yeast two-hybrid-assay. In addition, phosphorylation assays showed that SAPK10 exhibits autophosphorylation activity on the 177th serine, enabling it to phosphorylate WRKY87. OsWRKY87 functioned as a transcriptional initiator, according to a yeast one-hybrid assay and a luciferase assay. Remarkably, gel mobility shift assay showed that phosphorylated WRKY87 enhances its DNA-binding ability to the W-box cis-element of ABF1 promoter and activated its transcription, thereby elevating the ABF1 transcription and improving drought and salinity tolerance. Overall, our findings revealed a novel ‘SAPK10- WRKY87-ABF1’ module, which synergistically interacts to improve drought and salt tolerance in rice (Oryza sativa).
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